1. Field of the Invention
The invention relates to a weather-resistant exterior building material made of a novel constituent material, and an exterior article making use of the same.
2. Description of the Related Art
Most conventional building materials used in exterior articles are wood, and painting and the like are generally applied thereto because they get wet in the rain. However, there has been involved a risk of breakage and so forth occurring thereto because they become brittle after they get rotten and undergo deformation, and so forth, due to their inability to withstand usage over many years. There has also been the need for providing touch-up painting because of deterioration in the external appearance thereof due to cracking and peel-off occurring to outer faces thereof. Further, there have been problems with them in that they become slippery and dangerous to handle when wetted in the rain, and become difficult to handle because water drops on the outer faces continue to stay thereon without being absorbed or evaporated.
Also, there have been cases where an open veranda and a veranda are built with concrete or the like, however, these have had drawbacks rendering them unpopular, such as slipperiness due to lack of absorbability, and very heavy weight thereof.
It is therefore an object of the invention to solve some of the drawbacks of the conventional building materials as described above, and to provide a weather-resistant building material which has been unavailable in the past when light weight, weather resistance, corrosion resistance, characteristics of keeping away harmful insects such as white ants, insusceptibility to variation in temperature, hygroscopicity, and easiness in fabrication are taken into account, and an exterior article making use of the same.
The weather-resistant building material and the exterior article made up of the same make use of RB ceramic, CRB ceramic or fire-resistant CRB ceramic. The RB ceramic, the CRB ceramic or the fire-resistant CRB ceramic is a constituent material produced by the following method.
An attempt to obtain a carbonaceous material by utilizing rice bran, produced in a quantity of 900,000 tons a year in Japan and in a quantity of as much as 33 million tons a year throughout the world, has been well known by researches carried out by Mr. Kazuo Hokkirigawa, the first inventor of the invention (refer to “Functional Material”, May issue, 1997, Vol. 17, No. 5, pp. 24˜28).
In this literature reference is made to a carbon material (hereinafter referred to as the RB ceramic) and the preparation thereof, in which the material is obtained by mixing and kneading defatted bran derived from rice bran and the thermosetting resin together followed by drying a compact obtained by pressure forming and subsequently, baking the dried compact in an atmosphere of an inert gas.
With such a method of forming the RB ceramic as described above, however, it has been practically difficult to form the compact with high precision because there occurs a discrepancy in dimensions by as much as 25% in terms of a contraction ratio of the dimensions of the compact obtained by pressure forming to those of a finished compact obtained after baking the former in the inert gas. However, another ceramic (the CRB ceramic) representing an improvement on the RB ceramic has since been developed.
The CRB ceramic used in the invention is an improved material of the RB ceramic that is obtained from defatted bran derived from rice bran, and a thermosetting resin . More particularly, the defatted bran derived from rice bran and a thermosetting resin are mixed and kneaded and subjected to a primary baking in an inert gas at a temperature in a range of 700 to 1000° C., and pulverizing the kneaded mixture after the primary baking into carbonized powders passing through a sieve of 60 mesh or below. The carbonized powder and the thermosetting resin are further mixed and kneaded, and pressure formed at a pressure in a range of 20 to 30 MPa, subjecting the compact again to a heat treatment in an inert gas atmosphere at a temperature in a range of 100 to 1100° C. The CRB ceramic differs largely from the RB ceramic in that, in contrast with the RB ceramic having the contraction ratio of the dimensions of the compact obtained by pressure forming to those of the finished compact at as high as 25%, the CRB ceramic is superior to the RB ceramic in respect of the contraction ratio at not more than 3%, which is very low.
Further, with the invention, use can be made of material obtained by replacing part of the carbonized powders of the CRB ceramic with ceramic powders before subjecting the same to a secondary heat treatment. Such material utilizing the ceramic powders in combination with the CRB ceramic is referred to as the fire-resistant CRB ceramic.
The ceramic powders are composed of any selected from the group consisting of SiO2, Si3N4, ZrO2, Al2O3, SiC, BN, WC, TiC, Sialon (Si—Al—O—N based compound solid solution), porcelain clay, feldspathic clay, kaolin, and so forth.
With the invention, use can be made of one kind of, or not less than two kinds of the ceramic powders described above, and a blending ratio thereof at 30 to 100 by weight to the carbonized powders at 100 is adequate.